The invention is adapted especially to be used in a multiple-ratio, geared transmission of the kind disclosed in U.S. Pat. No. 5,150,297, dated Sep. 22, 1992. That patent is owned by the assignee of the present invention.
The control system of the '297 patent is adapted to be used with a multiple-ratio vehicle transaxle in an automotive vehicle driveline having an internal combustion engine with an adjustable throttle. The control system of the '297 patent has three shift valves that are actuated by three solenoid actuators. The shift valves are controlled by the actuators in a predetermined pattern to effect three ratio changes between the low ratio and an intermediate ratio, between an intermediate ratio and a direct-drive ratio, and between a direct-drive ratio and an overdrive ratio. The actuators respond to driveline variables so that the ratio changes can occur to meet operating demands as determined by sensors that detect, for example, vehicle speed, engine torque, drive range selector position, and engine operating temperature, as well as other variables.
The controllers are responsive to signals developed at the output driver portion of an electronic microprocessor, the input portion of which receives the signals from the driveline sensors.
The microprocessor includes diagnostic control modules for performing diagnostic strategies that detect when a control problem exists. A control problem may be the result of a hydraulic failure, a mechanical failure or an electronic failure. If failures of these kind are detected, error codes for the software may be called out by a service technician and proper repair action can be undertaken.
A control system of the kind disclosed in the '297 patent application has a valve system that cooperates with solenoid valve actuators. A change in state of the solenoid actuators results in a predictable shift response. The solenoid actuators operate in a predetermined sequence in order to effect a given ratio change.